Patent Document 1 (shown below) discloses a variable displacement pump capable of changing a discharge flow rate in a state in which the rotational speed thereof is fixed. This variable displacement pump includes two suction ports and two discharge ports, and is configured to be capable of switching between a full capacity operation in a state in which the two discharge ports are completely shut off from the two suction ports, and a half capacity operation in a state in which one of the discharge ports is communicated with the suction ports. In the half capacity operation, the discharge flow rate is equal to half of that in the full capacity operation under the condition of the same rotational speed. This variable displacement pump is incorporated in a hydraulic controller of an automatic transmission for a vehicle, and is driven by an internal combustion engine that drives the vehicle. The variable displacement pump supplies hydraulic oil (hydraulic pressure) necessary for a hydraulic actuator provided in the hydraulic controller.